Automatic faucets and bathroom flushers have been used for many years. An automatic faucet typically includes an optical or other sensor that detects the presence of an object, and an automatic valve that turns water on and off, based on a signal from the sensor. An automatic faucet may include a mixing valve connected to a source of hot and cold water for providing a proper mixing ratio of the delivered hot and cold water after water actuation. The use of automatic faucets conserves water and promotes hand washing, and thus good hygiene. Similarly, automatic bathroom flushers include a sensor and a flush valve connected to a source of water for flushing a toilet or urinal after actuation. The use of automatic bathroom flushers generally improves cleanliness in public facilities.
In an automatic faucet, an optical or other sensor provides a control signal and a controller that, upon detection of an object located within a target region, provides a signal to open water flow. In an automatic bathroom flusher, an optical or other sensor provides a control signal to a controller after a user leaves the target region. Such systems work best if the object sensor is reasonably discriminating. An automatic faucet should respond to a user's hands, for instance, it should not respond to the sink at which the faucet is mounted, or to a paper towel thrown in the sink. Among the ways of making the system discriminate between the two it has been known to limit the target region in such a manner as to exclude the sink's location. However, a coat or another object can still provide a false trigger to the faucet. Similarly, this could happen to automatic flushers due to a movement of bathroom doors, or something similar.
An optical sensor includes a light source (usually an infra-red emitter) and a light detector sensitive to the IR wavelength of the light source. For faucets, the emitter and the detector (i.e., a receiver) can be mounted on the faucet spout near its outlet, or near the base of the spout. For flushers, the emitter and the detector may be mounted on the flusher body or on a bathroom wall. Alternatively, only optical lenses (instead of the emitter and the receiver) can be mounted on these elements. The lenses are coupled to one or several optical fibers for delivering light from the light source and to the light detector. The optical fiber delivers light to and from the emitter and the receiver mounted below the faucet.
In the optical sensor, the emitter power and/or the receiver sensitivity is limited to restrict the sensor's range to eliminate reflections from the sink, or from the bathroom walls or other installed objects. Specifically, the emitting beam should project on a valid target, normally clothing, or skin of human hands, and then a reflected beam is detected by the receiver. This kind of sensor relies on the reflectivity of a target's surface, and its emitting/receiving capabilities. Frequently, problems arise due to highly reflective doors and walls, mirrors, highly reflective sinks, the shape of different sinks, water in the sink, the colors and rough/shiny surfaces of fabrics, and moving users who are walking by but not using the facility. Mirrors, doors, walls, and sinks are not valid targets, although they may reflect more energy back to the receiver than rough surfaces at the right angle incidence. The reflection of valid targets such as various fabrics varies with their colors and the surface finish. Some kinds of fabrics absorb and scatter too much energy of the incident beam, so that less of a reflection is sent back to the receiver.
A large number of optical or other sensors are powered by a battery. Depending on the design, the emitter (or the receiver) may consume a large amount of power and thus deplete the battery over time (or require large batteries). The cost of battery replacement involves not only the cost of batteries, but more importantly the labor cost, which may be relatively high for skilled personnel.
There is still a need for an optical sensor for use with automatic faucets or automatic bathroom flushers that can operate for a long period of time without replacing the standard batteries. There is still a need for reliable sensors for use with automatic faucets or automatic bathroom flushers.